1. Field of the Invention
The present invention relates generally to image processing systems and methods and more specifically to image processing systems and methods for performing color management.
2. Description of the Related Art
The importance of color management systems cannot be over-emphasized. With color management systems, color reproduction devices such as scanners, monitors and output devices can be characterized to provide image settings for optimal reproduction. Recently, with widespread colorization of output devices, the importance of a color-management technology for managing color information has become increased. Since different color reproduction devices have different color-reproduction ranges, color image data for one device cannot be directly used in another device. Accordingly, conventional systems are used wherein color image data corresponding to an input color space of an input device is temporarily converted to an absolute intermediate (independent) color space prior to conversion to an output color space of an output device.
FIG. 1 illustrates image data output from the input color space of an input device to the output color space of an output device. Image data is output by using a source profile 202 of the input device to transform the image from the input color space 201 to an absolute color space 203 (intermediate color space). The absolute color space 203 is converted to an output color space 205 by using a destination profile 204. The source profile 202 is a profile based on characteristics of the input device and is used for converting the input color space 201 to the absolute color space 203. The destination profile 204 is a profile based on characteristics of the output device for converting the absolute color space 203 to the output color space 205. At present, standardized format ICC (International Color Consortium) profiles are used in many cases.
FIGS. 6A and 6B are look-up tables for converting between device-dependent CMYK space and device-independent L*a*b* space in accordance with standard ICC specifications. In FIG. 6A, the look-up table is used in a source profile to transform image data from CMYK to L*a*b* while the look-up table of FIG. 6B is used to transform image data from L*a*b* to CMYK in accordance with ICC specifications.
In general, input and output devices have standardized ICC profiles that are created by hardware device manufacturers to reflect device characteristics at the time of manufacture. However, since such device characteristics do change over time, ICC-profile-creating tools and calorimeters are provided to update or create new profiles to reflect current characteristics of the devices.
Color reproduction can be enhanced in a multifunction peripheral (MFP) having a printer used as an output device and a having a scanner used as an input device, by using the printer to output low to high density patches composed of primary colors (cyan, magenta, yellow), and then using the scanner to read the patches, and then performing primary color calibration. Although this technique enables desirable color matching for primary colors, it less effective for higher-order colors obtained by mixing a plurality of color materials.
Nevertheless, even in MFPs, and in particular, when the output device is an electrographic printer, high quality reproduction of color cannot be obtained due to rapid daily changes in device status (for example, the color and quality of output images rapidly change due to changes in device status compared with images output by the ink-jet printer), so that output images vary even if the same profile is used in the same device.
For the same reason, if a plurality of devices use the same profile to output the same data, each device outputs a different color image.
In addition, by using ICC-profile-creating tool and calorimeter, an ICC profile which matches a device status at that time can be created, so that an image can be output in desirable color. However, new profiles need to be created by first outputting numerous color patches and then measuring each and every color patch. This process is not only time-consuming, but it is also computation-intensive particularly for devices whose status often varies daily.